[TenTec] Eagle problem?

[Bob McGraw - K4TAX]

My first rule of engagement......."if it is a mike connect it to the mike 
input.  If it is not a mike then don't connect it to the mike input."

I recall that the Omni VI has an Audio Input on the rear.  This is the place 
to connect the audio data for the radio.  Now with that being said, in doing 
this one needs to terminate the audio line at the radio input with a 270 to 
470 ohm resistor.  There is already a 10K build out resistor on the inside. 
Adding  the R at the cable end effectively forms a L pad or attenuator. 
This R can be added physically inside the RCA connector on the cable or 
across the female RCA jack on the inside of the radio.  The objective is to 
get the signal level higher on the cable from the computer/interface to the 
radio thus improving the signal-to-noise ratio.  In this case the noise is 
RF.  Even a step further is to add some 10 to 20 dB attenuation in the form 
of a Pi attenuator at the connector end at the radio.  This will require the 
audio level to be raised at the computer/interface.

The MIC gain on the radio should operate about the 9 to 10 o'clock position. 
Be sure the Speech Processor is not active.  Set the radio for 100 watts and 
adjust the audio level from the computer/interface to produce some 35 watts 
of output.

I've used this very successfully on a Paragon, a Paragon II and two 
different Omni VI radios.  I also use VOX to handle the RX/TX switching.

73
Bob, K4TAX


----- Original Message ----- 
From: "Carter" <k8vt at ameritech.net>
To: <tentec at contesting.com>
Sent: Wednesday, May 14, 2014 3:35 PM
Subject: Re: [TenTec] Eagle problem?


> On 5/8/2014 6:51 PM, Stuart Rohre wrote:
>
>> These types of problems usually  indicate that there is RF leaking
> > back to any any transceiver he might try, because his antenna is too
> > close to the shack ...
>
> An interesting thought, but can we always blame the "antenna being too 
> close to the shack"?
>
> I bought my Omni VI new in 1994 and have never been able to operate SSB or 
> PSK31, SSTV or any other mode that required the use of the mic jack. (Good 
> thing I am 99% a CW and RTTY guy.  <grin> ) Anything over about 10 (ten) 
> watts of power seems to cause the problem, utter and complete distortion 
> of the radiated signal.
>
> The shack is in the basement, the antenna is a 132' long dipole about 25 
> feet high and fed with ladder (window) line to a Johnson KW Matchbox 
> tuner. The length of the window line between the Matchbox and the hole in 
> the wall where it exits the basement is no more than five feet. Yes, when 
> I measure the RF current in each leg of the window line they are 
> different -- to be expected as this is not a perfect world and the dipole 
> is not in free space. The coax cable to the Centurion / Omni VI has a 
> multiple ferrite bead balun.
>
> After years of unsuccessfully chasing around with ferrite beads and 
> chokes, I was finally told [by ******] that my dipole was "too close to 
> the house". Unfortunately, because of the shape of the lot, the location 
> of trees and zoning/deed restrictions, the antenna HAS to be where it is.
>
> So...problem occurs at around 10 watts of output, the antenna can't be 
> moved and I don't think I am the only ham in the world using a dipole 
> close to the house fed with window line.
>
> This leads me to do the unthinkable and to ask about the elephant in the 
> room. Rather than everyone saying the antenna "is too close to the house", 
> is it possible that this particular vintage of Omni VI option 3 is just 
> particularly sensitive to RF getting into the mic jack (or other ports)??? 
> Is this unique to my radio? Do Yaecomwoods suffer from the same issue?
>
> The reason I ask is that I am getting into PSK31, JT9 and JT65-HF (and 
> yes, I realize these are "low power" modes), but I wouldn't mind going up 
> to 20 or 25 watts -- or  SSTV at (gasp!)100 watts.
>
> I would appreciate any thoughts or suggestions. New /different radio or 
> fixing this radio (how?) is OK, but a 100' tower 300' away is just not an 
> option.
>
> 73,
> Carter   K8VT
>
>
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